Actually, while I'm clearing out a stall in my barn for the horse now; I think the rider deserves some credit. At the original stumble and peck at the first fence of the complex, he slips his reins and sits *still* - that allowed this fabulous horse to find his fifth leg and jump. Any clutching or interfering by the rider at that point surely would have resulted in a rotational fall. Throughout the whole sequence, once it's gone terribly wrong, the rider stays quiet and out of the horse's way - the rider "taking over" at any point would have had a bad result.
Second, consider the trust relationship this horse and rider must have. Badly unbalanced, no reins, no stirrups - the rider is steering with his eye, not interfering, and trusting that the horse will figure it out. And the horse must have absolutely trusted that his rider was not going to interfere with his heroic efforts.
Extraordinary video, and it really makes the point of why it's important that event horses think for themselves and jump independently and not constantly helf precisely between the rider's leg and hand.